Understanding the mechanisms of grapevine decline

What are the challenges caused by grapevine trunk diseases?

Grapevine trunk diseases (GTDs) are caused by a variety of pathogens, and they are one of the major causes of grapevine decline (i.e., decreased yields and rootstock mortality). The effects of GTDs have been particularly bad over the last 20 years because we lack efficacious treatment methods.

Many facets of the interactions between grapevines, environmental conditions, and GTDs remain unexplored, leaving gaps in our understanding of foliar symptoms, notably those caused by esca.

Many facets of the interactions between grapevines, environmental conditions, and GTDs remain unexplored

Because of technical constraints, we have rarely been able to test the hypotheses put forth to explain why esca erratically causes foliar symptoms in grapevines. The greatest difficulty is that we have been unable to elicit these foliar symptoms under controlled conditions. However, understanding disease etiology is essential if we wish to develop growing practices that effectively prevent and/or control GTDs.

What experimental approaches have you used in your research?

We adopted two creative approaches to surmount these scientific obstacles.

First, we set up experiments using older plants obtained from a vineyard that had been hit by esca. These plants were transported from the vineyard to the laboratory in pots and studied under controlled conditions. Second, we performed X-ray microtomography at the SOLEIL synchrotron facility, which allowed us to directly and non-invasively observe the vascular systems of the rootstock. This collaborative and interdisciplinary project allowed us to test, for the first time ever, whether hydraulic dysfunction was associated with esca's foliar symptoms, as hypothesised elsewhere. We used an approach that combined plant pathology and physiology.

What are the broader implications of your results?

In our field of research, the main challenge is identifying the exact sequence of events that precedes the drop in yield and plant death, notably the loss of leaves and berries. We also need to have a better understanding of the viticultural practices and environmental conditions that influence the development of these diseases. To this end, we must shift the paradigm. Instead of viewing grapevine decline as a disease, and notably as a GTD, we need to see it as a systemic problem caused by a set of interacting factors.

The project is part of the French National Plan for Vineyard Decline [Plan national de dépérissement du vignoble], which is funded by the Ministry for Agriculture and Food